Hydrocarbon conversion apparatus



sept; 9, 1958 F. E. FR'EY ETAL HYDROCARBON CONVERSION APPARATUS OriginalFiled Jan. 25, 1952 BYMMM A TTORNEVS Unid Sift-Liles Patent O 2,851,339HYDROCARBON CONVERSION APPARATUSl Original application January 25, 1952,Serial No. 268,162, now Patent No. 2,803,684, dated August 20, 1957.

Divided and this application May 11, 1956, Serial No. 584,221

7 Claims. (Cl. 234-260) This invention relates to the alkylationof'hydrocan bons. In one of its aspects the inventionrelatesto animproved process for the aromatization of. hydrocarbons employing `animproved pebble heater apparatus. Inanother `aspect of the invention itrelates to the utilization of the gaseous products or residue gas froman aromatization process. In still another of its aspects the inventionrelates to the use' of said gaseous products or. residue gas with littleor no purification for the alkylation of hydrocarbons. In still afurther aspect the invention relates to a catalyticalkylation process inwhich certain gases. containing the desired alkylating agent andl anyundesirable acetylene resulting from a hydrocarbon conversion. operationare employed while avoiding catalyst deterioration which ordinarilyvwould bev caused by the use ofth'e said gases without al prio-1'purification'. ln stllanotheraspect the` invention'v makes economicallyfeasible thefuse of a process for the preparation of benzene', and1other aromatics, by cracking hydrocarbons at elevatedtemperatu'res forextended periods yof time, by virtue of it's particular alkylationprocess aspect. The preparation of benzene and aromatics by' crackinghaving been thus rendered economically feasible, the advantages of thecombination process are further increased by virtue of its pebblehe'ateraspect, all as will appear from a consideration of: that which follows.lication' isa division of our co- This app pending application SerialNo. 268,162, filed January 25,

1952,- now Patent No. 2,803,684; Y

It is well known that benzene a'nd" other aromatics are formed whenhydrocarbons are cracked at e'levatedf'teirl'- peraturesfor' extendedperiods of` time. In thepast this process hasi not? been foundprofitable' because the4 yield or aromatics is not great enough tosupport thei operation alone, andno ready salel otherthan'asifuelexistedfbr'the gaseous productsprodueed.

We' have discovered that the gaseous products produced when hydrocarbonsare cracked to aromatics, especially as in the pebble heater operation',for-"example, at temperatures in the range 1300-l900 F., preferably1475-1675 F., Whichis set forth' and described herein',V aro-wellad'apt'ed to the? production of d-iisopropyl Withflittle ornofpuriiication. These` gases comprise; hydrogen,v methane' andethylene,- Wth minor amounts ofV acetylene, propyleneand higher-boilinghydrocarbons Paten-t No, 2,534,089 issued December l2,` 1950, disclosesand claims a pebble heater. Other 'patentsV directeclr yto pebbleheaters are also extant.

When reacted withisobutane in theY presence of. V,an AlCl3 catalystethylene is converted into diisopropyl: with an efficiency- -as high as85 percent.` Propyleneis also alkylated, but the alkylate produced. isofl'conside'vrably poorer quality" than the ethylene' alkylate; The'sai'dminor .amcuntor low propylene' content of thegaseous products,

" the gases;

`made 'and/or used according to this invention, therefore L Ice2,851,33h

Patented Sept. 9, 1958 2. however,. to. free theresidue gas of C4andheavierv hydrocarbons.

It should also be notedthat 4in thealkylation of isoparainswith .lightlolens, in the, presence ofaluminum chloride-hydrocarbon complexcatalyst, the acetylene or like relatively very active materials such asbutadiene and the like, even when present in a certainminitnurn amount,have such af pronounced and deleterious effect on the catalyst that its.activity to maintain olefin conversion is decreased.` Thus, it has beenfound that each pound of acetylene entering a reactor in which a mixedethylenepropylene feed 'is being alkylated with isobutane will'renderinactive approximately 4'pounds of aluminum chloride for the productionof diisopropyl. Propylene also appears to'have a similar but lesspronounced effect. The presence ofbutenes is. also deleterious. In thecase of excessive prop'ylene or butene not only is aluminum chlorideconsumption increased'but'thecatalyst may become sufficientlyviscous torender the'process inoperative.

The relatively very active materials to which reference has'b'eenmade`are acetylene, butadiene, butenes and the like; Other such materialsmaybe present as indicated. Forl ex`amplea gas stream resulting from thecracking of a light hydrocarbon gas, or from the severe cracking -of ahydrocarbon oil, will bea' cracked gas lcontaining ethane, propane ornormal butane along' withV acetylene, methylacetylene, allene(prop'adcne) andthe like; Some of the gaseswhich areundesirable in thesense'thatthey cause deterioration of/the'catalyst willv do so eventhough presentf in' ratherv minorquantities; It' should beconsideredthatf the constant addition to thel catalyst of even.averyfsmall'percentage' of such gasesresults,l over aperiod of time; inank accumulation *off undesirable material upon, in-or in'A combinationwith the catalyst.

According to the invention described and claimed in copendingIapplication, Serial No. 2781566; filed` March 26'; 1952, now Patent No.2,781,409, by the instant inventorsgithasfbeen found thatithe presenceof a certain proportionlof hydrogenin the feed gases'to the alkylationstep serves-toprevent Iotherwise undesirable deterioration or" otheradverse'elfect upon the catalyst which is dueto theracetylene or otherreactive hydrocarbons and therefore the hydrogen 'in the gases isretained and fed therewith to thealkylation zone. Inv the'event thatinsufcient hydrogenis: present in said gas for the purpose of the: said`invention, additionalv hydrogen` can be added to Inview ofthe inventionof the above-mentioned applithe gases resulting from an aromatizationprocess, .according to theA present inventionare usable in an ensuingalkylation operation, which renders thearomatization, as hereindescribedand claimed, economically feasible.

According tothe present invention there is provided .an improved pebbleheater and treater combination for the cracking of hydrocarbons toproduce aromatics. Also, according to the invention, the gases thusproduced can be. used in an alkylation step as and `-in the mannerdescribedzandclaimed herein. Therefore, as `a further feature ofthepresent invention there is provided an improved combination. of apebble heater and treater incombination. with. an limproved alkylationVoperation which, is profvided directly with the gases resulting fromsaid cracking.

Referringnow to'the drawing, which shows diagram` .matically in modifiedform a pebble heater and treater combinatiomcf the invention, incombination with an heated'to a desired temperature, for example, in theneighborhood of 1500 F. and then is` passed through conduit 4 intosoaker 5` wherein aromatization is cornpleted, following which thecracked stock vapors are passed through conduit 6 into pebble preheater7 wherein simultaneously there are effected preheating of pebblestherein and passing therethrough as well as a preliminary cooling of thecracked and aromatized vapors, the pebbles also serving asl a iilter toat least partly remove coke and tar which, as will be seen, aresubsequently burned, thus providing some heat for the process. Thevapors are removed from pebble preheater 7 through conduit 8 and passedto tower 9, to which reference will be made hereinafter. Preheatedpebbles coated with some coke and tar are passed from pebble preheater 7through conduit 10 into pebble heater 11 wherein the pebbles aresimultaneously heated for use in heater 3 and denuded of whatever cokeand tar accumulation they possess. The heated pebbles are then passedthrough conduit 12 into the pebble cracking heater 3. Pebbles which havegiven up heat in heater 3 are circulated in known manner from heater 3by means of diagrammatically illustrated apparatus 14, 15, 16, and 17 topebble preheater 7 and pebble heater 11 respectively. Thediagrammatically illustrated apparatus can be a bucket elevator, gaslift or other equivalent means.

Returning to tower 9, there is provided an oil quench 49 in the tower tomaintain the tower bottom at about 400 F. or other suitable temperaturesto separate tar which is removed through conduit 13. Overhead from tower9 passes through conduit 18 into tower 19 wherein there is employed aquench 20 which can be similar to that employed in tower 9. Thetemperature at the bottom of tower 19 is maintained at about 100 F. orsome other suitable temperature so that lighter products will be removedor taken off as overhead from tower 19 and passed through conduit 21 toscrubber system 22, in which light liquid products are removed from thegases. Liquid products are drawn olf through conduit 23 and the gasesare passed through conduit 24 to alkylation reactor 25 in which saidgases are contacted with a preponderant proportion of isobutane eitheradded to the system through conduit 26 and/or recycled to reactor 25through conduit 27, 26, and 24. Etiluent from reactor 25 is passedthrough conduit 28 to settler 29 in which a gas phase, a hydrocarbonphase and a catalyst phase are formed. The gas phase is withdrawnthrough line 50 and passed to a vapor recovery system not shown. Aportion of this gas may be recycled to reactor 25 if desired, thoughthis is usually not done. Catalyst is withdrawn from settler 29 throughconduit 30 and is recycled through conduit 31 and 32 to reactor 25.Continuously or intermittently some of the catalyst coming from settler29 can be withdrawn through conduit 33 for refortication or discard asdesired. Also fresh catalyst, or ingredients thereof, can be added tothe system through conduit 34. The hydrocarbon phase formed in settler29 is withdrawn therefrom through conduit 35. A portion of thehydrocarbon effluent is recycled through conduit 36, and cooling meansnot shown, to conduit 26 and by way of conduit 24 to reactor 25 tocontrol the temperature therein. The remainder of the efuent fromsettler 29 is passed into a caustic treater 37 from which it is passedthrough conduit 38 to fractionator 39 from which C3 and lighter gasesare taken off as overhead through conduit 40. The bottoms fromfractionator 39 are withdrawn through conduit 41 and passed tofractionator 42 in which isobutane is separated from alkylate productand returned to the process through conduit 27 while alkylate product isremoved through conduit 43.

The material for quenches 49 and 20 can be supplied from any suitablesource but preferably is supplied employing the bottoms from tower 19,the said bottoms being withdrawn therefrom through conduit 45 and beingpassed by means of pump 46 and cooler 47 to quenches 49 and 20. Anyexcess quench stock can be withdrawn through conduit 48. The excessquench liquid carried in line 48 may be combined with the liquidproducts from line 23 and passed to a purification zone, not shown. Fromthis stream, the aromatic products, benzene, toluene, xylene, etc., willbe obtained, as well as cyclopentadiene and butadiene.

The catalysts which can be employed in the process of the invention arewell known in the art. Thus in the reactor 25 there is maintained analuminum halide-hydrocarbon complex catalyst activated as known in theart with a hydrogen halide. The catalyst usually is made up usingaluminum chloride. As indicated above, fresh catalyst can be addedperiodically or continuously to the mass of catalyst in circulation inthe process and a portion of the mass can be withdrawn therefrom inorder to maintain a constant desired activity of catalyst. The hydrogenhalide usually will be hydrogen chloride, either added as such, orproduced in situ, using a corresponding quantity of water or in othersuitable manner.

To more fully describe the invention, a hydrocarbon gas comprisingethane, propane, or butane is cracked in a pebble heater having 6' I. D.X 7 pebble heating zone in which pebbles are heated by countercurrentcontact with hot combustion gases, whose temperature ranges from about1450 F. upwards, preferably 1800 F. to about 2600 F., depending upon theother conditions. The cracking zone in which the feed gas is contactedcountercurrently with hot pebbles from the heating zone is 4% I. D. x 6.Preheated steam may be used in the dome of the cracking chamber tominimize carbon formation if desired. Conditions of temperature,throughput and pebble flow are adjusted so that the olefin content ofthe cracked gas entering soaking chamber 5 is maximum or slightly below,as shown in Table I under Cracked Gas Composition for n-butane, propaneand an ethane-propane mixture. The soaking chamber is a 7 x l0'insulated vessel and operates at approximately 1550 F. and 3.8 p. s. i.g. pressure. Residence time is approximately 3.9 seconds. The hot gas iscooled to 900 to l000 F. by countercurrent contact with moving pebblesin chamber 7 and further quenched in 9 and 19 as previously mentioned.Aromatic tar, substantially free of toluene and lower-boiling aromatics,is withdrawn at 13.

The residue gas, free of C4 and heaviers, but containing acetylene andother reactive hydrocarbons, is cornpressed to 420 p. s. i. g. andcharged to the reactor which is equipped with an eicient stirrer.Isobutane in the amount of 4 mols per mol of olefin, recirculatedhydrocarbon in amount to control temperature rise across the reactor toabout 5 F. and catalyst amounting to about V2 the volume of the totalhydrocarbon feed are also charged to the reactor. Reaction temperatureis 110 F., pressure 400 and time 20 minutes. Hydrogen is present duringthe reaction.

In soaking drum 5, sufficient time is provided to permit thearomatics-forming step to be effected. The reaction time required varieswith temperature. Temperatures may range upwards from about 1250 F.,preferably upwards of about 1300 F. Short reaction times result inliquid products containing up to 50 percent of olens and diolefns,including cyclopentadiene, relatively small tar yields, and in additionrelatively large amounts of ethylene in the gaseous products. Very longreaction times result in low unsaturation in the volatile aromatic oils,which may reach 90 percent benzene and 7 percent toluene, high yields oftar and carbon, and relatively small yields of ethylene. Normally weprefer to operate the aromatics-forming step at intermediate conditionsof time-temperature, and at pressures below about 50 p. s. i. g. Underthese conditions, an aromatic light oil containing about percent benzeneis produced, tar production is reduced and high ethylene yieldsareobtained. The relation between time and temperature to 5 produce thedesired Adegree ofieracking is given by vthe following equation:

where t is time in seconds and T is reaction temperature in F.

Table I records data exemplifying the operation of the logro t(see`)(9.1 :1:03)

over-al1 combination of the invention.

Table I Cracking Step:

Feed Stock. ..-g. n-Bu- Propane Cs-Ca tane I g Mixture 1 Feed tocracking zone, lb./day 120, 000 118,000 319,000 Pebble circulation,lb./hr e ....v 5, 000 35,000 35, 000 Vol. iuel gas (1,000 B. t. iL/c.

c. f./hr s 16,000 16,000 16, 000 Combustion temperature, 2, 400 2, 4002, 400 Vol. preheated steam to crac 111g i Cracked Ges Composition, MolPer'- cent:

Soaking time, sec 3. 9 3. 6 3 1 Benzol Cut:

Vol. gal/day 2, 700 2, 500 2, 050 Approximate Composition, Wt.

Percent- C and lighter 6. C5 unsaturate-.. 1. Benzene 82. C1 unsaturate.0. Toluene 9. 5 Aromatic tar, gah/day 1, 650 1, 530 1, 380 .alkylationStep:

Olen Feed (Residue Gas from Cracking Step)- Volume, M. c. f./day 1, 8002,060 2, 600 Total olen, lb 31, 000 29, 700 31, 500 Composition, M01Percent:

2 17.1 23. 4 30. 5 01:14---- 59. 1 57. 1 53. 2 C2H2-.. O. 8 0. 6 0. 402H 20. 6 16. 9 14. 3 03H11 2. 4 2. 0 1.

Isobntane (gek/day)- Fresh feed 12, 900 12,200 13,700 Recycle 38, 00036, 800 38, 500 Hydrocarbon recirculation (gal./

day) 470, 000 450, 000 500, 000 Catalyst cireu lation (gal/day) 273, 000262, 000 289,000 AlCh (1b/day) 750 715 790 Reaction Conditions- Reactiontemp., F" c 110 110 110 Reaction pressure, p. 400 400 400 Alkylate(gaL/day) 13, 500 12,900 14, 200

% methane, 20% ethane, 74% propane and 1% butane.

An incidental but nevertheless extremely important advantage of theinvention resides in the elimination of expensive equipment forseparating hydrogen, methane, etc. The cost of gas compression isrelatively low and the requirement for gas compression in the process islow. Hydrogen is thus introduced into the alkylation reactor, and hasthe desirable eiect of increasing catalyst life by minimizing adverseeffects of reactive hydrocarbons, particularly of acetylenes, butadieneand the like. This effect makes possible still further simplification ofthe gas puriiicationsystem, since removal of acetylene and the lasttraces of butadiene is unnecessary. The net result, therefore, is aconsiderable simplification of the process, coupled with increasedefficiency and enhanced catalyst life.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure and the appended claims to the invention, theessence of which is that a novel and considerably improved pebble heaterand treater combination for the cracking of hydrocarbons to producearomatics and other valuable products has been provided and that gasesresulting. from the said cracking of hydrocarbons to` form aromatichydrocarbons are utilized in an alkylation operation as described,thereby making economically feasible the said aromatic hydrocarbonforming operation.

We claim:

l. Hydrocarbon conversion apparatus comprising, in combination: meansfor heating hydrocarbons to an aromatization temperature by contact'-vvith pebbles; means for introducing said hydrocarbons to saidiirstmentioned means; means for withdrawing' thus heated hydrocarbonsfrom said first-mentioned means; means for maintaining thus' withdrawnhydrocarbons under aromatization conditions for a substantial length-oftime out of contact with pebbles; means' for countercurrently contactingthus aromatized products with relatively co'ol pebbles; means for'further heating th'us contacted pebbles; and means' for supplying thusheated pebbles to said means for heating hydrocarbons.

2. Hydrocarbon conversion apparatus comprising, in combination: meansforV heating' hydrocarbons to an aromatiia'tion temperature by' ContactWith pebbles; means for introducing s'a'id hydrocarbons 'to said`iirl'stmentioned means; means for withdrawing thus heated hydrocarbons'from said first-mentioned means; means for maintaining thus heatedhydrocarbons u'nde'r ar'omatization conditions for a substantial lengthof time out of contact with pebbles; means for countercurrentlycontacting thus aromatized products with relatively cool pebbles; meansfor further heating thus contacted pebbles; means for supplying thusheated pebbles to said means for heating hydrocarbons; and means forpassing pebbles from said means for heating hydrocarbons to said meansfor further heating pebbles and to said means for contacting aromatizedproducts with pebbles.

3. Improved pebble heater apparatus comprising, in combination; apebble-heating chamber positioned above a hydrocarbon-heating chamber;conduit means establishing communication between said chambers; asoaking chamber in communication with said hydrocarbon-heating chamber;a quench chamber in communication with said pebble`heating chamber, saidquench chamber adapted to receive gaseous products from said soakingchamber and countercurrently contact the same with relatively coolpebbles; conveying means for moving pebbles from saidhydrocarbon-heating chamber to said quench chamber and to saidpebble-heating chamber; means for transferring pebbles from said quenchchamber to said pebble-heating chamber; means for supplying hydrocarbonfeed to said hydrocarbon-heating chamber; means for heating pebbles insaid pebble-heating chamber; and means for withdrawing hydrocarbon fromsaid quench chamber.

4. Improved pebble heater apparatus comprising, in combination: a pebblepreheating chamber; means, associated with said pebble preheatingchamber, for countercurrently contacting pebbles with hot combustiongas; a hydrocarbon-heating chamber positioned below said pebblepreheating chamber; a pebble conduit establishing communication betweensaid chambers and adapted to permit gravitational ilow of pebbles fromsaid pebble preheating chamber into the upper part of saidhydrocarbonheating chamber; means for introducing fluid into a lowerpart of `said hydrocarbon-heating chamber; a soaking chamber.; gasconduit means establishing communication between the upper part of saidhydrocarbon-heating chamber and said soaking chamber; a quench chamber;gas conduit means establishing communication between the lower part ofsaid quench chamber and said soaking chamber; gas outlet means in anupper part of said quench chamber; pebble conduit means for transferringpebbles from the lower part of said quench chamber into said pebblepreheating chamber; and elevator means adapted to move pebbles from thelower part of said hydrocarbonheating chamber tothe upper part of saidpebble preheating chamber and to the upper part of said quench chamber.

5. An improved pebbleheater apparatus, suitable for the production ofaromatic hydrocarbons by cracking, which comprises, in combination: apebble heating chamber, a cracking chamber connected to vsaid pebbleheating chamber in a manner such that heated pebbles from said chambercan be passed to said cracking chamber, means for introducing fluid intothe lower part of said cracking chamber, a soaking chamberl connected tosaid cracking chamber so that cracked vapors from said cracking chambercan be passed to said soaking chamber, a pebble preheating chamberconnected to said soaking chamber in a manner such that vaporsl fromsaid soaking chamber can be passed countercurrently to said pebblepreheating chamber, whichis adapted to cool hydrocarbon vapors from saidsoaking chamber, the said pebble preheating chamber being connected withsaid pebble heating chamber in such a manner that preheated pebbles fromSaid preheating chamber can be passed to said pebble heating chamber.

6. An apparatus according to claim 5 wherein there is provided a meansfor conveying pebbles from said cracking chamber to one of said pebblepreheating and pebble heating chambers.

7. Means for the production of aromatic hydrocarbons by cracking whichcomprises, in combination: a pebble heating chamber in which pebbles areheated to a temperature sufciently high to transfer heat to hydrocarbonsto be cracked in heat exchange contact therewith as describedhereinafter; a cracking chamber connected with said pebble heatingchamber in which pebbles heated Ias described above are contacted inheat exchange relationship with said hydrocarbons to crack the same;means for introducing fluid to said cracking chamber; means forwithdrawing thus heated hydrocarbons from said cracking chamber; asoaking chamber connected with said cracking chamber for retainingcracked vapors from said cracking chamber for a period of time sulcientto complete aromatization of the said cracked vapors; a pebblepreheating chamber connected with said soaking chamber, for heatingpebbles, to be passed countercurrently to said pebble heating chamber,in heat exchange relation with vapors from said soaking chamber, and tothereby cool the said vapors contacted therewith; said pebble preheatingchamber being connected with said pebble heating chamber in such amanner that preheated pebbles from said pebble preheating chamber can bepassed to said pebble heating chamber.

References Cited in the file of this patent UNITED STATES PATENTS2,555,210 Waddill et al. May 29, 1951

1. HYDROCARBON CONVERSION APPARATUS COMPRISING, IN COMBINATION: MEANSFOR, HEATING HYDROCARBONS TO AN AROMATIZATION TEMPERATURE BY CONTACTWITH PEBBLES; MEANS FOR INTRODUCING SAID HYDROCARBONS TO SIDFIRSTMENTIONED MEANS; MEANS FOR WITHDRAWING THUS HEATED HYDROCARBONSFROM SAID FIRST-MENTIONED MEANS, MEANS FOR MAINTAINING THUS WITHDRAWNHYDROCARBONS UNDER AROMATIZATION CONDITIONS FOR A SUBSTANTIAL LENGTH OFTIME OUT OF CONTACT WITH PEBBLES; MEANS FOR COUNTERCURRENTLY CONTACTINGTHUS AROMATIZED PRODUCTS WITH RELATIVELY COOL PEBBLES; MEANS FOR FURTHERHEATING THUS CONTACTED PEB-